Non-destructive write/read leveling

ABSTRACT

In some examples, a memory device is configured with non-volatile memory array(s) having one or more associated volatile memory arrays. The memory device may include a non-destructive write mode configured to prevent access to the non-volatile memory array(s) during an initiation or calibration sequence performed by the memory device or an electronic device associated with the memory device to calibrate read and write access timing associated with the memory device.

RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.61/868,221 to Andre et al., entitled “Non-Destructive Write/ReadLeveling Using User Accessible Register,” filed Aug. 21, 2013, thecontents of which are incorporated herein by reference in theirentirety.

BACKGROUND

When a memory device is activated, the memory device may perform acalibration or an initialization sequence. The calibration orinitialization sequence may require reading and writing test data to andfrom multiple memory arrays. Unfortunately, in some types of memorydevices, the writing or reading of test data to the memory arrays duringthe calibration or initialization sequence may result in unintentionaloverwriting of data stored in the memory arrays.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical components or features.

FIG. 1 illustrates an example block diagram of select components of amemory device including non-volatile memory arrays and volatile memoryarrays for preventing reads/writes to the non-volatile memory arraysduring calibration or initialization of the memory device.

FIG. 2 illustrates another example block diagram of select components ofa memory device for preventing reads/writes to the non-volatile memoryarrays during calibration or initialization of the memory device.

FIG. 3 illustrates yet another example block diagram of selectcomponents of a memory device for preventing reads/writes to thenon-volatile memory arrays during calibration or initialization of thememory device.

FIG. 4 is a flow diagram showing an illustrative process for performingwrite based calibration or write based initialization of a memory deviceand maintaining data stored in one or more non-volatile memory arrays.

FIG. 5 is a flow diagram showing an illustrative process for performingread based calibration or read based initialization of a memory deviceand maintaining data stored in one or more non-volatile memory arrays.

DETAILED DESCRIPTION

This disclosure includes, in part, techniques and implementations toimprove the reliability of memory devices. For example, this disclosureincludes improved systems and methods for initializing or calibratingmemory devices including non-volatile or “permanent” storage capable ofmaintaining data when a power supply is deactivated (e.g., magneticmemories or magnetic random access memories or MRAMs).

In general, memory devices, such as random access memories (RAMs)perform a calibration or initialization sequence to adjust the timingrequirements associated with reading data from the memory device andwriting data to the memory device. The initialization process mayinvolve calibrating a write time and a read time by, for example,writing and reading predetermined data sets into the memory arrays.Unfortunately, in some cases, memory devices that include non-volatilememory arrays may be utilized by an electronic device to storeexecutable code and persistent data, in addition to or in lieu of theelectronic device's disk drives, as memory devices that includenon-volatile memory arrays are also capable of maintaining data when thepower supply is deactivated.

When the non-volatile memory arrays store executable code or dataintended to persist through the deactivation of the memory device, theexecutable code or persistent data may be partially or completelyoverwritten by the calibration data during the initialization sequence,potentially resulting in errors, loss of data, and/or data corruption.Therefore, in some implementations described herein, an individualnon-volatile memory array is paired with a volatile memory array, suchthat data may be read from and written to the volatile memory arrayduring the calibration or initialization process without overwriting thedata stored in the non-volatile memory arrays. In some cases, the memorydevices may be configured to include control circuitry that may routeactivate and precharge commands to the non-volatile memory arrays andmay route read and write commands to the volatile memory arrays. In thismanner, data may be transferred to and from the non-volatile memoryarray to the volatile memory array and to and from the volatile memoryarray to a cache or other external location and the calibration orinitialization sequence of the memory device may be performed via readand write commands issued to the volatile memory arrays withoutaffecting the data stored in the non-volatile memory arrays.

In other implementations, the memory device may be configured to includeone or more registers to activate and deactivate a non-destructive writemode and/or a non-destructive read mode to prevent overwriting of datastored in the non-volatile memory arrays. For example, the memory devicemay include one or more user accessible or programmable registers thatmay allow a user or external source to configure the non-destructivewrite mode and/or the non-destructive read mode of operation for thememory device. In some cases, in addition to preventing read/writeaccess during the initialization or calibration process, the user mayutilize the register to place the memory device into the non-destructivewrite mode and/or a non-destructive read mode during standard operationsof the memory device (for example, to test the memory device).

In other examples, the memory device may be configured to default to thenon-destructive write mode (for instance, via a initializationregister), in response to a power up of the memory device and to exitthe non-destructive write mode following a signal from control circuitryindicating that the calibration or initialization sequence is complete.In some examples, the register may include one or more initialization ormode registers, one or more user or externally accessible registers, oneor more flip flops, latches, or other storage elements.

In some implementations, the status of the non-destructive write modeand/or a non-destructive read mode may be controlled by a state machinethat implements the operations of disabling reading and/or writing datato/from the non-volatile memory arrays. For example, the state machinemay set one or more values based on the status of the initialization orcalibration sequence, the state of the power supply, and/or the state ofthe memory device.

In some particular implementations, the one or more registerscontrolling access to the non-volatile memory arrays may be placedwithin a data path and/or configured to operate with circuitryassociated with normal operations of the memory device, such as datapaths, command line paths, and/or addressing circuitry. For example, theregisters may be located on the command line path between the controlcircuitry and each of the non-volatile memory arrays.

FIG. 1 illustrates an example block diagram of select components of amemory device 100 including and non-volatile memory arrays 108, 110, and112 and volatile memory arrays 102, 104 and 106 for preventingread/writes to the non-volatile memory arrays 108, 110, and 112 duringcalibration or initialization of the memory device 100. In someexamples, the memory device 100 may include removable and/ornon-removable media implemented in various types of technology forstorage of information such as computer-readable instructions ormodules, data structures, program modules or other data. Suchcomputer-readable media may include, but is not limited to, RAM, ROM,EEPROM, flash memory or other computer-readable media technology, solidstate storage, RAID storage systems, storage arrays, network attachedstorage, storage area networks, cloud storage, or any other medium thatmay be used to store information. In some particular implementations,the non-volatile memory array may include elements of magnetic memoriesor magnetic random access memories (MRAMs), such as magnetic memorycells or magnetic disk storage.

In general, the memory device 100 may be an example of tangiblenon-transitory computer storage media including both temporary orvolatile memory arrays 102, 104, and 106 and permanent or non-volatilememory arrays 108, 110, and 112. In the illustrated example, each of thenon-volatile memory arrays 108, 110, and 112 are associated with acorresponding one of the volatile memory arrays 102, 104 and 106, suchthat when data that is stored in the non-volatile memory arrays 108,110, and 112 is being accessed by an external source 114 (e.g., one ormore circuits associated with the electronic device accessing the memorydevice 100) the data may first be stored in the corresponding orassociated volatile memory arrays 102, 104, and 106 to protect the datastored in the non-volatile memory arrays 108, 110, and 112 frominadvertent or unnecessary modifications and/or deletions. For example,the non-volatile memory array 108 (identified as “Non-Volatile MemoryArray(1)”) is associated with the volatile memory array 102 (identifiedas “Volatile Memory Array(1)”).

In the illustrated example, three non-volatile arrays 108, 110, and 112and three associated volatile memory arrays 108, 110, and 112 are shown.However, it should be understood that the memory device 100 may bearranged with an alternative number of non-volatile memory arrays and analternative number of volatile memory arrays. Additionally, in someimplementations, there may not be a one to one correspondence betweenthe non-volatile memory arrays and the volatile memory arrays. Forinstance, a single volatile memory array may be associated with two ormore non-volatile memory arrays, such that when data is read from thecorresponding non-volatile memory arrays the data is copied ortransferred to the volatile memory array before the external source 114is permitted to access or edit the data. For example, volatile memoryarray(1) 102 may be associated with both non-volatile memory array(1)108 and non-volatile memory array(2) 110.

In some examples, the control circuitry 116 is configured to receivevarious commands from the external source 114. For example, the externalsource 114 may issue activate commands to cause data stored in thenon-volatile memory arrays 108, 110, and 112 of the memory device 100 tobe loaded into the associated volatile memory arrays 102, 104, and 106and/or into one or more caches (not shown) accessible to the externalsource 114. In other examples, the external source 114 may issueprecharge commands to cause the data stored in the volatile memoryarrays 102, 104, and 106 or in the cache accessible to the externalsource 114 to be written back into the non-volatile memory arrays 108,110, and 112 in order to prepare the cache for receiving another blockof data. In some examples, the control circuitry 116 may receive a readcommand and/or a write command from the external source 114 to accessand/or modify the data stored in the volatile memory arrays 102, 104,and 106 or in the cache accessible to the external source 114.

In some implementations, a mode register associated with the controlcircuitry 116 may be configured to activate and deactivate anon-destructive write mode and/or a non-destructive read mode. In someexamples, when the non-destructive modes are active, data access (e.g.,loads and writes backs) between the non-volatile memory arrays 108, 110,and 112 and the volatile memory arrays 102, 104, and 106 are prevented,as indicated by dashed lines 118, 120, and 122. In this manner, thecalibration or initialization sequence may be performed by the controlcircuitry 116 and/or the external source 114 by reading and writing datainto the volatile memory arrays 102, 104, and 106 without overwriting orintroducing other errors into the non-volatile arrays 108, 110, and 112.

In other implementations, the non-destructive write mode and/or thenon-destructive read mode may be configured to prevent operationsassociated with select control signals or commands, such as theprecharge and activate commands, from being performed in conjunctionwith the non-volatile memory arrays 108, 110, and 112 and/or thevolatile memory arrays 102, 104, and 106. For instance, in someimplementations, a precharge command may cause data stored in thevolatile memory arrays 102, 104, and 106 to be transferred or written tothe non-volatile memory arrays 108, 110, and 112. The read and writecommands may allow the external source 114 to access and/or edit thedata stored in the volatile memory arrays 102, 104, and 106. Thus, insome examples, the mode register associated with the control circuitry116 may be configured to activate and deactivate the non-destructivewrite mode and/or the non-destructive read mode to prevent operationsassociated with select control signals and/or commands from beingcarried out or performed by the memory arrays 102-112.

In one particular example, when the non-destructive write mode and/orthe non-destructive read mode is active, the memory device 100, thememory arrays 102-112, and/or the control circuitry 116 may beconfigured to ignore operations associated with the precharge andactivate commands, while performing operations associated with the readand write commands. In this manner, the calibration or initializationsequence may read and write data into the volatile memory arrays 102,104, and 106 without overwriting or introducing other errors into thenon-volatile memory arrays 108, 110, and 112. In some particularimplementations, the non-destructive write mode may be utilized withouta non-destructive read mode, such that the memory device 100 may beconfigured to allow the data to be loaded from the non-volatile memoryarrays 108, 110, and 112 but prevent data from being written back to thenon-volatile memory arrays 108, 110, and 112.

In some examples, the mode register configured to activate anddeactivate the non-destructive write mode and/or the non-destructiveread mode may be one or more externally accessible or user programmableregisters that may allow a user or the external source 114 to set anoperating mode for the memory device 100. In some cases, in addition topreventing load/write back access to the non-volatile memory arrays 108,110, and 112 during the initialization or calibration process, the moderegister may prevent access to the non-volatile memory arrays 108, 110,and 112 during standard operations of the memory device 100, forinstance, during a test or maintenance mode. In other examples, the moderegister may be an initialization register configured to default to thenon-destructive write mode and/or a non-destructive read mode inresponse to a power up of the memory device 100 and to exit thenon-destructive write mode and/or the non-destructive read modefollowing a signal from the control circuitry 116 indicating that thecalibration or initialization sequence is complete. In some examples,the mode register may include one or more flip flops, latches, or otherstorage elements.

In some implementations, the condition of the non-destructive write modeand/or the non-destructive read mode may be controlled by a statemachine associated with the control circuitry 116 that implements theoperations of disabling reading data from the non-volatile memory arrays108, 110, and 112 and/or writing data to the non-volatile memory arrays108, 110, and 112. For example, the state machine may set one or morevalues based on the status of the initialization or calibrationsequence, the state of a power supply (not shown), and/or the state ofthe memory device 100.

In some particular implementations, the mode register may be placedwithin a data path and/or configured to operate with circuitryassociated with normal operations of the memory device, such as datapaths, command line paths, and/or addressing circuitry. For example, theregister(s) may be located on the command line path between the controlcircuitry 116 and each of the non-volatile memory arrays 108, 110, and112, as illustrated below with respect to FIG. 2.

FIG. 2 illustrates another example block diagram of select components ofa memory device 200 for preventing reads and/or writes to a non-volatilememory array 202 during calibration or initialization of the memorydevice 200. In the illustrated example, circuitry, data paths, andcontrol paths are shown with respect to the non-volatile memory array202 and a corresponding volatile memory array 204. However, it should beunderstood that the memory device 200 may include any number ofnon-volatile memory arrays and volatile memory arrays, as describedabove with respect to FIG. 1.

In the illustrated example, the memory device 200 includes controlcircuitry 206 configured to receive activate/precharge commands 208 andread/write commands 210 from an external source 212 accessing datastored in the non-volatile memory array 202. In some cases, the controlcircuitry 206 may include row selection circuitry, column selectioncircuitry, sense amplifiers, write drivers, and/or charge pumps, amongother circuits for operating a memory device.

In general, the read/write commands 210 are received by the controlcircuitry 206 and routed to the volatile memory array 204, such that theexternal source 212 is able to access data 214 stored within thevolatile memory array 204. Similarly, the activate/precharge commands208 are received by the control circuitry 206 and routed to thenon-volatile memory array 202 via one or more registers 216.

In general, the data 214 may be transferred between the non-volatilememory array 202 and the volatile memory array 204. The external source212 may be configured to access the data 214 once the data 214 has beentransferred from the non-volatile memory array 202 and stored within thevolatile memory array 204. Thus, in some examples, the non-volatilememory array 204 may act as a cache for storing the data 214 while thedata is being accessed by the external source 212. In other examples,the external source 212 may be configured to access the data 214 whenthe data 214 is stored in a cache (not shown), and the volatile memoryarray 204 may store the data 214 while the data 214 is being writtenback to or loaded from the non-volatile memory array 202 to preventerrors which may be introduced, for instance, if a power failure occursduring a write operation associated with the non-volatile memory array202.

The register(s) 216 may be configured to activate and deactivate anon-destructive write mode. In some examples, when the non-destructivewrite mode is active, the register(s) 216 may prevent theactivate/precharge commands from reaching the non-volatile memory array202, which in turn may prevent the data 214 stored within thenon-volatile memory array 202 from being accessed by the external source212.

In some examples, the register(s) 216 may be one or more user accessibleor programmable registers to allow a user or the external source 212 toset a write mode of operating for the memory device 200. In otherexamples, the register(s) 216 may be an initialization registerconfigured to default to the non-destructive write mode, in response toa power up of the memory device 200 and to exit the non-destructivewrite mode following a signal from the control circuitry 206 or theexternal source 212 indicating that the calibration or initializationsequence is complete. In some examples, the register(s) 216 may includeone or more flip flops, latches, or other storage elements that may beconfigured to decouple the control circuitry 206 from the non-volatilememory array 202.

In the illustrated example, the register(s) 216 may prevent both theactivate and precharge commands 208 from reaching the non-volatilememory array 202, thereby preventing the associated activate andprecharge operations from being performed on the non-volatile memoryarray 202. However, in other examples, the register(s) 216 may beconfigured to prevent the operations associated with the prechargecommands from being carried out at the non-volatile memory array 202,while allowing the operations associated with the activate commands tobe carried out at the non-volatile memory array 202 (e.g., data may betransferred from the non-volatile memory array 202 to the volatile array204 but data may be prevented from being transferred from the volatilearray 204 to the non-volatile memory array 202). In this manner, theregister(s) 216 may set the non-destructive write mode to prevent thedata 214 from being written back to the non-volatile memory array 202,while allowing the data 214 to be loaded from non-volatile memory array202.

While FIG. 2 depicts one or more registers 216 configured to implement anon-destructive write mode during the initialization or calibrationprocess of the memory device 200, it should be understood that one ormore registers 216 may be placed within a command path to implement thenon-destructive write mode of a memory device including multiplenon-volatile memory arrays, as illustrated below with respect to FIG. 3.

FIG. 3 illustrates yet another example block diagram of selectcomponents of a memory device 300 for preventing read/writes to thenon-volatile memory arrays 302, 304, and 306 during calibration orinitialization of the memory device 300. As described above with respectto FIG. 2, an external source 308 may issue activate and/or prechargecommands 310 that are received by control circuitry 312 of the memorydevice 300. The control circuitry 312 may then route theactivate/precharge commands 310 or may issue access commands to one ormore of the non-volatile memory arrays 302, 304, and 306.

In the illustrated example, one or more registers 314 are positioned ina command path to implement a non-destructive write mode in order toprevent access or writes to data stored in the non-volatile memoryarrays 302, 304, and 306 when the non-destructive write mode is active.For example, the memory device 300 may perform a calibration orinitialization sequence to adjust the timing requirements with regardsto reading and writing data from the memory device 300 upon anactivation or power up of the memory device 300. The calibration processinvolves writing and reading predetermined data sets into thenon-volatile memory arrays 302, 304, and 306. As explained above, insome cases, this could cause the data stored in the non-volatile memoryarrays 302, 304, and 306 to be inadvertently overwritten.

In the illustrated example, the one or more registers 314 may preventthe activate and precharge commands 310 from reaching the non-volatilememory arrays 302, 304, and 306 when the non-destructive write mode isenabled and may allow the activate and precharge commands 310 to reachthe non-volatile memory arrays 302, 304, and 306 when thenon-destructive write mode is disabled. The illustrated example alsoshows routing circuitry 316 configured to route the activate andprecharge commands 310 (or access commands) to the correspondingnon-volatile memory array 302, 304, and 306. In other examples, therouting circuitry 316 may be removed or incorporated into the controlcircuitry 312, for instance, when a register 314 is associated with eachof the memory arrays 302, 304, and 306, as described above with respectto FIG. 2.

FIG. 4 is a flow diagram illustrating an example process implementingnon-destructive write mode during initialization or calibration sequenceof a memory device. The process is illustrated as a collection of blocksin a logical flow diagram, which represents a sequence of operations,some or all of which can be implemented in hardware, software or acombination thereof. In the context of software, the blocks representcomputer-executable instructions stored on one or more computer-readablemedia that, which when executed by one or more processors, perform therecited operations. Generally, computer-executable instructions includeroutines, programs, objects, components, data structures and the likethat perform particular functions or implement particular abstract datatypes.

The order in which the operations are described should not be construedas a limitation. Any number of the described blocks can be combined inany order and/or in parallel to implement the process, or alternativeprocesses, and not all of the blocks need be executed. For discussionpurposes, the processes herein are described with reference to theframeworks, architectures and environments described in the examplesherein, although the processes may be implemented in a wide variety ofother frameworks, architectures or environments.

FIG. 4 is a flow diagram showing an illustrative process 400 forperforming write based calibration or write based initialization of amemory device and maintaining data stored in one or more non-volatilememory arrays. In general, a memory device may perform a write basedcalibration or write based initialization sequence to adjust the timingwith regards to reading and writing data from the memory device uponinitialization or power up of the memory device. The calibration processtypically involves writing and reading predetermined data sets into thememory arrays. Unfortunately, in some cases, memory devices havingnon-volatile memory arrays may be utilized by an electronic device tostore executable code, in addition to or in lieu of the electronicdevices disk drives, as the memory devices are capable of maintainingdata when the power supply is deactivated and the calibration processmay inadvertently cause the excitable code to be overwritten, as mayexternal sources expect the memory arrays to be non-initializedfollowing power off periods.

Thus, in some cases, when the arrays of a memory device store executablecode or data intended to persist through the deactivation of the memorydevice, the executable code or persistent data may be partially orcompletely overwritten by the calibration data during the initializationsequence, potentially resulting in errors, loss of data, and/orcorruption of the code. Therefore, a volatile memory array may be pairedwith each of the non-volatile memory arrays in the memory device, suchthat data may be loaded from and written back to the volatile memoryarrays during initialization or calibration without overwriting the datastored in the non-volatile array.

In some cases, the memory devices may be configured to include controlcircuitry that may route activate and precharge commands to thenon-volatile memory arrays and that may route read and write commands tothe volatile memory arrays, such that data may transferred to and fromthe non-volatile array to the volatile array and to and from thevolatile array to a cache or other external location. In this manner,the calibration or initialization sequence of the memory device may beperformed via read and write commands issued to the volatile memoryarrays without affecting the data stored in the non-volatile memoryarrays.

In some examples, the memory device may also include one or moreregisters to prevent activate and precharge operations from beingperformed during initialization or calibration. For instance, the memorydevice may include one or more user accessible or programmable registersthat may allow a user or an external source to set a write mode ofoperating that prevents access to the data stored in the non-volatilememory arrays. In other examples, the memory device may be configured todefault to a non-destructive write mode (for instance, via aninitialization register), in response to a power up of the memory deviceand to exit the non-destructive write mode following a signal fromcontrol circuitry indicating that the calibration or initializationsequence is complete. In some examples, the register(s) may include oneor more initialization or mode registers, one or more user accessibleregisters, one or more flip flops, latches, or other storage elements.

At 402, the process 400 includes disabling write back to non-volatilememory. For example, a user or an external source may cause one or moreregisters to be set indicating to the memory device that the memorydevice is in a non-destructive write mode and/or a non-destructive readmode. In other examples, the memory device may include one or moreinitialization registers that default to the non-destructive write modeand/or the non-destructive read mode in response to an activation of thememory device or an associated electronic device. In some particularexamples, the register may cause the memory device to enter anon-destructive write mode, allowing reads to be performed with regardsto the non-volatile memory arrays.

In general, when the non-destructive write mode and/or thenon-destructive read mode are enabled, the memory device prevents accessto the non-volatile memory arrays, while allowing read and write accessto volatile memory arrays. For example, the memory device may includepairs of non-volatile memory arrays and volatile memory arrays, forinstance, to assist in preventing errors from occurring in thenon-volatile memory arrays when a write is in progress during a powerfailure or other interruption of the memory device. Thus, in someimplementations, the non-destructive write mode and/or thenon-destructive read mode may allow an external source to read and writethe predetermined data sets into the volatile or temporary memory arraysduring the initialization or calibration sequence in order to calibratetiming requirements with respect to reading and writing data to thememory device without affecting the data stored in the non-volatilememory arrays.

At 404, the process 400 includes performing temporary writes to memory.For example, the memory device may receive commands to write data, andthe memory device may allow the writes to the temporary memory arrays(e.g., the volatile memory arrays) and may prevent the writes to thenon-volatile memory arrays. For example, during the calibrationsequence, the external source may issue write commands to writepredetermined data into the memory device. In some examples, while thenon-destructive write mode and/or the non-destructive read mode isactive (and write back is disabled to the non-volatile memory arrays),the memory device may route the write command to volatile or temporarymemory, thus preventing the data in the non-volatile memory arrays frombeing inadvertently overwritten.

At 406, the process 400 includes performing reads to temporary memory.For example, the memory device may receive commands to read data, andthe memory device may allow the reads to the temporary memory arrays,while preventing access to the non-volatile memory arrays. As describedabove, during the calibration sequence, the external source may issueread commands to read the predetermined data written into the memorydevice (at 404). In some examples, while the non-destructive write modeand/or the non-destructive read mode is active (and reads are disabledto the non-volatile memory arrays), the memory device may route the readcommand to volatile or temporary memory, thus preventing the data in thenon-volatile memory arrays from being accessed. In other examples, thememory device may disable the data transfer between the volatile ortemporary memory arrays and non-volatile memory arrays, such that whenthe precharge and activate commands are received by the memory device nodata is transferred between the temporary or volatile memory arrays andthe non-volatile memory arrays.

At 408, the process 400 includes determining whether the timing iscorrect. For example, the external source and/or the memory device maydetermine if the timing is correct. To illustrate, when the timingassociated with reading data is being calculated, predetermined data maybe written into the temporary memory (e.g., at 404) and then the dataread from the temporary memory array (e.g., at 406) may be compared withthe predetermined data to determine if the timing is correct. Forexample, with respect to the read timing, if the data that is read fromthe temporary memory array matches the predetermined data that iswritten to the temporary memory array, then the timing is correct. Ifthe timing is correct, the process 400 may proceed to 410. However, ifthe timing is incorrect, the process 400 advances to 412 in order toadjust the read timing. The process 400 then returns to 404. In thismanner, the external source may calibrate the timing requirementsassociated with the memory device by reading and writing data to thetemporary memory arrays without inadvertently overwriting the datastored in the non-volatile memory arrays.

At 410, the process 400 includes enabling write back to non-volatilememory. For example, the memory device and/or the external source mayre-enable the write back to the non-volitale memory arrays. Toillustrate, the external source may enable the write back in response todetermining that the write and the read timing is correct. In otherexamples, the write back may be enabled and/or the non-destructive writemode and/or the non-destructive read mode may be disabled upon acompletion of the calibration sequence and/or the initializationsequence of the memory device. In some specific examples, the writes maybe enabled and/or the non-destructive write mode and/or thenon-destructive read mode may be disabled in response to the completionof a power up or initialization sequence of an electronic deviceassociated with the memory device.

FIG. 5 is a flow diagram showing an illustrative process for performingread based calibration or read based initialization of a memory deviceand maintaining data stored in one or more non-volatile memory arrays.In general, a memory device may perform a read based calibration or readbased initialization sequence to adjust the timing with regards toreading and/or writing data from the memory device upon initializationor power up of the memory device. The calibration process typicallyinvolves writing and reading predetermined data sets into the memoryarrays. Unfortunately, in some cases, memory devices having non-volatilememory arrays may be utilized by an electronic device to storeexecutable code, in addition to or in lieu of the electronic devicesdisk drives, as the memory devices are capable of maintaining data whenthe power supply is deactivated and the calibration process mayinadvertently cause the excitable code to be overwritten, as mayexternal sources expect the memory arrays to be non-initializedfollowing power off periods.

Thus, in some cases, when the arrays of a memory device store executablecode or data intended to persist through the deactivation of the memorydevice, the executable code or persistent data may be partially orcompletely overwritten by the calibration data during the initializationsequence, potentially resulting in errors, loss of data, and/orcorruption of the code. Therefore, a volatile memory array may be pairedwith each of the non-volatile memory arrays in the memory device, suchthat data may be loaded from and written back to the volatile memoryarrays during initialization or calibration without overwriting the datastored in the non-volatile array.

In some cases, the memory devices may be configured to include controlcircuitry that may route activate and precharge commands to thenon-volatile memory arrays and that may route read and write commands tothe volatile memory arrays, such that data may transferred to and fromthe non-volatile array to the volatile array and to and from thevolatile array to a cache or other external location. In this manner,the calibration or initialization sequence of the memory device may beperformed via read and write commands issued to the volatile memoryarrays without affecting the data stored in the non-volatile memoryarrays.

In some examples, the memory device may also include one or moreregisters to prevent activate and precharge operations from beingperformed during initialization or calibration. For instance, the memorydevice may include one or more user accessible or programmable registersthat may allow a user or an external source to set a write mode ofoperating that prevents access to the data stored in the non-volatilememory arrays. In other examples, the memory device may be configured todefault to a non-destructive write mode (for instance, via aninitialization register), in response to a power up of the memory deviceand to exit the non-destructive write mode following a signal fromcontrol circuitry indicating that the calibration or initializationsequence is complete. In some examples, the register(s) may include oneor more initialization or mode registers, one or more user accessibleregisters, one or more flip flops, latches, or other storage elements.

At 502, the process 500 includes disabling write back to non-volatilememory. For example, a user or an external source may cause one or moreregisters to be set indicating to the memory device that the memorydevice is in a non-destructive write mode and/or a non-destructive readmode. In other examples, the memory device may include one or moreinitialization registers that default to the non-destructive write modeand/or the non-destructive read mode in response to an activation of thememory device or an associated electronic device. In some particularexamples, the register may cause the memory device to enter anon-destructive write mode, allowing reads to be performed with regardsto the non-volatile memory arrays.

In general, when the non-destructive write mode and/or thenon-destructive read mode are enabled, the memory device prevents accessto the non-volatile memory arrays, while allowing read and write accessto volatile memory arrays. For example, the memory device may includepairs of non-volatile memory arrays and volatile memory arrays, forinstance, to assist in preventing errors from occurring in thenon-volatile memory arrays when a write is in progress during a powerfailure or other interruption of the memory device. Thus, in someimplementations, the non-destructive write mode and/or thenon-destructive read mode may allow an external source to read and writethe predetermined data sets into the volatile or temporary memory arraysduring the initialization or calibration sequence in order to calibratetiming requirements with respect to reading and writing data to thememory device without affecting the data stored in the non-volatilememory arrays.

At 504, the process 500 includes performing temporary writes to memory.For example, the memory device may receive commands to write data, andthe memory device may allow the writes to the temporary memory arrays(e.g., the volatile memory arrays) and may prevent the writes to thenon-volatile memory arrays. For example, during the calibrationsequence, the external source may issue write commands to writepredetermined data into the memory device. In some examples, while thenon-destructive write mode and/or the non-destructive read mode isactive (and write back is disabled to the non-volatile memory arrays),the memory device may route the write command to volatile or temporarymemory, thus preventing the data in the non-volatile memory arrays frombeing inadvertently overwritten.

At 506, the process 500 includes performing reads to temporary memory.For example, the memory device may receive commands to read data, andthe memory device may allow the reads to the temporary memory arrays,while preventing access to the non-volatile memory arrays. As describedabove, during the calibration sequence, the external source may issueread commands to read the predetermined data written into the memorydevice (at 504). In some examples, while the non-destructive write modeand/or the non-destructive read mode is active (and reads are disabledto the non-volatile memory arrays), the memory device may route the readcommand to volatile or temporary memory, thus preventing the data in thenon-volatile memory arrays from being accessed. In other examples, thememory device may disable the data transfer between the volatile ortemporary memory arrays and non-volatile memory arrays, such that whenthe precharge and activate commands are received by the memory device nodata is transferred between the temporary or volatile memory arrays andthe non-volatile memory arrays.

At 508, the process 500 includes determining whether the timing iscorrect. For example, the external source and/or the memory device maydetermine if the timing is correct. To illustrate, when the timingassociated with reading data is being calculated, predetermined data maybe written into the temporary memory (e.g., at 504) and then the dataread from the temporary memory array (e.g., at 506) may be compared withthe predetermined data to determine if the timing is correct. Forexample, with respect to the read timing, if the data that is read fromthe temporary memory array matches the predetermined data that iswritten to the temporary memory array, then the timing is correct. Ifthe timing is correct, the process 500 may proceed to 510. However, ifthe timing is incorrect, the process 500 advances to 512 in order toadjust the read timing. The process 500 then returns to 506. In thismanner, the external source may calibrate the timing requirementsassociated with the memory device by repeatedly adjusting timing at 512and re-reading data at 506 to the temporary memory arrays withoutinadvertently overwriting the data stored in the non-volatile memoryarrays.

At 510, the process 500 includes enabling write back to non-volatilememory. For example, the memory device and/or the external source mayre-enable the write back to the non-volitale memory arrays. Toillustrate, the external source may enable the write back in response todetermining that the write and the read timing is correct. In otherexamples, the write back may be enabled and/or the non-destructive writemode and/or the non-destructive read mode may be disabled upon acompletion of the calibration sequence and/or the initializationsequence of the memory device. In some specific examples, the writes maybe enabled and/or the non-destructive write mode and/or thenon-destructive read mode may be disabled in response to the completionof a power up or initialization sequence of an electronic deviceassociated with the memory device.

Although the subject matter has been described in language specific tostructural features, it is to be understood that the subject matterdefined in the appended claims is not necessarily limited to thespecific features described. Rather, the specific features are disclosedas illustrative forms of implementing the claims.

1-20. (canceled)
 21. A memory device, comprising: an array ofnon-volatile memory cells; volatile storage elements coupled to thearray of non-volatile memory cells; a register that stores a value,wherein the value determines that the memory device is in one of anormal operation mode and a non-destructive operation mode; controlcircuitry coupled to the array of non-volatile memory cells, thevolatile storage elements, and the register, wherein the controlcircuitry is configured to: when the value stored in the registerindicates that the memory device is in normal operation mode: inresponse to a precharge command received by the memory device, transferdata stored in the volatile storage elements into the array ofnon-volatile memory cells; and when the value stored in the registerindicates that the memory device is in the non-destructive mode ofoperation: in response to the precharge command received by the memorydevice, block writes to the array of non-volatile memory cells such thatdata stored in the volatile storage elements does not over-write datastored in the array of non-volatile memory cells.
 22. The memory deviceof claim 21, wherein the array of non-volatile memory cells is an arrayof magnetic random access memory cells.
 23. The memory device of claim21, wherein the control circuitry is further configured to: when thevalue stored in the register indicates that the memory device is innormal operation mode: in response to an activate command received bythe memory device, transfer data stored in the array of non-volatilememory cells into the volatile storage elements; and when the valuestored in the register indicates that the memory device is in thenon-destructive mode of operation: in response to the activate commandreceived by the memory device, block reads from the array ofnon-volatile memory cells.
 24. The memory device of claim 21, wherein,upon power up or reset, the value stored in the register indicates thatthe memory device is in the non-destructive operation mode.
 25. Thememory device of claim 24, wherein the memory device is configured toexit from the non-destructive operation mode automatically aftercompletion of a calibration procedure associated with at least one ofread timing and write timing.
 26. The memory device of claim 21, whereinthe register is a programmable register that is programmed in responseto a command received by the memory device.
 27. The memory device ofclaim 21, wherein the control circuitry is further configured to: whenthe value stored in the register indicates that the memory device is inthe non-destructive mode of operation: in response to a write commandreceived by the memory device, write data received by the memory devicecorresponding to the write command into the volatile storage elementswithout overwriting data stored in the array of non-volatile memorycells.
 28. The memory device of claim 21, wherein the memory deviceincludes a write leveling mode in which timing adjustment correspondingto a data strobe signal and a clock occurs, wherein during the writeleveling mode, the memory device is configured to output levelingfeedback.
 29. The memory device of claim 21, wherein the value in theregister is set to indicate the non-destructive operation mode inresponse to initiation of a calibration or initialization sequence toadjust timing requirements associated with reading data from the memorydevice or writing data to the memory device.
 30. A memory device,comprising: an array of memory cells; storage elements coupled to thearray of memory cells; a register that stores a value, wherein the valuedetermines that the memory device is in one of a normal operation modeand a non-destructive operation mode; control circuitry coupled to thearray of memory cells, the storage elements, and the register, whereinthe control circuitry is configured to: when the value stored in theregister indicates that the memory device is in normal operation mode:in response to a precharge command received by the memory device,transfer data stored in the storage elements into the array of memorycells; and in response to an activate command received by the memorydevice, transfer data stored in the array of memory cells into thestorage elements; and when the value stored in the register indicatesthat the memory device is in the non-destructive mode of operation:ignore operations associated with precharge and activate commands. 31.The memory device of claim 30, wherein the control circuitry is furtherconfigured to: when the value stored in the register indicates that thememory device is in the non-destructive mode of operation: performoperations associated with read and write commands, wherein theoperations associated with read and write commands access data stored inthe storage elements while blocking writes to the array of memory cells.32. The memory device of claim 31, wherein the non-destructive mode ofoperation corresponds to a calibration in which write operations areused for calibration of write timing, wherein the control circuitry isfurther configured to: when the value stored in the register indicatesthat the memory device is in the non-destructive mode of operation:block writes to the array of memory cells so that the write operationsduring calibration do not over-write data stored in the array of memorycells.
 33. The memory device of claim 30, wherein the register is aprogrammable register, and wherein the value is stored in theprogrammable register in response to a command received by the memorydevice from a memory controller.
 34. The memory device of claim 30,wherein the storage elements are in a cache.
 35. The memory device ofclaim 30, wherein the storage elements are volatile storage elements,and wherein the array of memory cells is an array of non-volatile memorycells.
 36. The memory device of claim 30, wherein the memory device isconfigured to default to the non-destructive operation mode in responseto a power up of the memory device.
 37. The memory device of claim 30,wherein the memory device includes a write leveling mode in which timingadjustment corresponding to a data strobe signal and a clock occurs,wherein during the write leveling mode, the memory device is configuredto output leveling feedback.
 38. A system, comprising: a memorycontroller; and a memory device coupled to the memory controller,wherein the memory device includes: an array of memory cells; storageelements coupled to the array of memory cells; a programmable registerthat stores a value, wherein the value determines that the memory deviceis in one of a normal operation mode and a non-destructive operationmode, wherein the value in the programmable register is programmed inresponse to a command from the memory controller; control circuitrycoupled to the array of memory cells, the storage elements, and theregister, wherein the control circuitry is configured to: when the valuestored in the register indicates that the memory device is in normaloperation mode: in response to a precharge command received by thememory device, transfer data stored in the storage elements into thearray of memory cells; and in response to an activate command receivedby the memory device, transfer data stored in the array of memory cellsinto the storage elements; and when the value stored in the registerindicates that the memory device is in the non-destructive mode ofoperation: block writes to the array of memory cells.
 39. The system ofclaim 38, wherein the memory controller initiates a calibration sequencethat includes writing data to the memory device while the memory deviceis in the non-destructive operation mode.
 40. The system of claim 39,wherein data written to the memory device during calibration is writtento the storage elements so that write operations during calibration donot over-write data stored in the array of memory cells.